The invention relates to an article of orthopaedic footwear constructed of plastics material, and to a method of making such an article.
A number of processes for making orthopaedic footwear are already known, but these result in articles which have a very limited life. Furthermore, the articles produced are not adaptable to the wide range of deformities which are met with in practice; i.e. each article of footwear is made to an individual design.
The present invention provides an article of orthopaedic footwear comprising an upper secured to a sole, the upper being of thermosoftening plastics material and having a lining of resilient expanded thermosoftening plastics material of closed cell construction, in which the upper has an autogenously welded seam covered externally by a strip of thermosoftening plastics material autogenously welded to the upper on both sides of the seam.
This article of footwear thus has a particularly strong seam construction. The article can be shaped to suit the patient, by forming and/or cutting the upper, without substantial restriction, since the seam construction is equally suitable for forming and cutting. For instance, if the article is in the form of a bootee, the seam being at the rear, the ankle portion and/or the heel portion can be formed and/or cut in order to suit the patient. Thus, articles in accordance with the invention can be supplied as stock items which can subsequently be adapted to the shape required.
The invention also provides a method of making the above article comprising vacuum-forming an upper from thermosoftening sheet plastics material having a lining of resilient expanded thermosoftening plastics material, autogenously welding the sheet plastics material by diathermy (high frequency heating) to form a seam, externally covering the seam with a strip of thermosoftening plastics material, autogenously welding the strip to the upper on both sides of the seam by diathermy, and securing the upper to a sole.
Preferably there is a longitudinal weld along each of the longitudinal edges of the strip. Alternatively or (preferably) additionally, there may be transverse welds spaced along the strip; if it is subsequently necessary to cut across the seam, the cut can be made along one of the transverse welds, so that there are no loose portions which might be weakened by flexing.
The article of footwear preferably has a removable insole of resilient expanded thermoplastic material. The insole can thus be removed from the article, shaped to the patient's foot, and replaced. A preferred insole comprises a top layer of lower density and a separate bottom layer of higher density.
The plastics material of the upper and of the strip is preferably a vinyl polymer, e.g. polyvinylchloride (PVC). The upper may have a backing of thermosoftening textile material bonded to the upper, between the upper and its lining. The expanded plastics material used in the article is preferably an expanded cross-linked polyethylene.
There may, of course, be more than one seam in the upper, each seam being covered by a strip as described above. For instance, there may be an seam at the toe and at the heel.